1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. The present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a driving method thereof, or a manufacturing method thereof. One embodiment of the present invention relates to a light-emitting device in which a transistor is provided in each pixel.
2. Description of the Related Art
In an active matrix light-emitting device including light-emitting elements, in general, at least a light-emitting element, a transistor (a switching transistor) that controls input of image signals to pixels, and a transistor (a driving transistor) that controls the value of current supplied to the light-emitting element in response to an image signal are provided in each pixel. In a light-emitting device having the above structure, drain current of a driving transistor is supplied to a light-emitting element; thus, when the threshold voltage of driving transistors varies among pixels, the luminance of light-emitting elements varies correspondingly.
Patent Document 1 discloses a display device in which the threshold voltage of a TFT (a driver element) is corrected inside a pixel so that variations in threshold voltages do not influence the luminance of a light-emitting element. Patent Document 2 to 4 disclose display devices for monitoring outside the pixels.